Prophylactic Enoxaparin Dosing After Bariatric Surgery: A Systematic Review and Meta-Analysis of Pharmacodynamic Efficacy and Safety

INTRODUCTION: Venous thromboembolism (VTE) remains a leading cause of preventable morbidity and mortality following metabolic bariatric surgery (MBS). Low-molecular-weight heparin (LMWH) is widely used for thromboprophylaxis; however, the optimal prophylactic enoxaparin dose in patients with obesity remains uncertain. Anti-factor Xa (anti-Xa) activity is commonly used as a surrogate marker of pharmacological efficacy. METHODS: A systematic review and meta-analysis was conducted in accordance with PRISMA guidelines and registered with PROSPERO. PubMed, EMBASE, the Cochrane Library, and ClinicalTrials.gov were searched from inception to 31 March 2026. Studies evaluating prophylactic enoxaparin dosing in patients with obesity undergoing MBS, with reported anti-Xa levels, were included. Random-effects meta-analyses compared lower (30-40 mg) versus higher (60 mg) enoxaparin regimens with respect to attainment of prophylactic anti-Xa levels with secondary outcomes including mean anti-Xa activity, VTE and bleeding event rates. RESULTS: Ten studies comprising 1,069 enrolled patients, of whom 1,016 contributed to the primary meta-analysis, met the inclusion criteria. There was no significant difference in the proportion of patients achieving prophylactic anti-Xa levels between higher and lower dose regimens (risk ratio 1.05, 95% CI 0.91-1.20; I² = 58.2%, p = 0.0104). Higher doses were associated with significantly increased mean anti-Xa levels (mean difference 0.13 IU/mL, 95% CI 0.05-0.21; p = 0.001). CONCLUSION: Higher prophylactic enoxaparin doses increase anti-Xa levels but do not improve attainment of prophylactic targets compared with standard dosing following MBS. In a post-hoc, exploratory, hypothesis-generating subgroup analysis, BMI-adjusted dosing strategies demonstrated comparable pharmacodynamic efficacy to fixed higher doses; this finding is not pre-specified and should not be used to support definitive conclusions. High-quality multicentre randomised trials are required to define optimal thromboprophylaxis strategies in this high-risk population.